Method for self-monitoring a ceramic pressure measuring cell of a capacitive pressure sensor and evaluation circuit for carrying out said method
a capacitive pressure sensor and ceramic pressure measurement technology, applied in fluid pressure measurement, fluid pressure measurement by electric/magnetic elements, instruments, etc., can solve problems such as unrecognised, aggravated problem, and ingress of medium pressur
Active Publication Date: 2013-10-17
IMF ELECTRONIC GMBH
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Benefits of technology
The invention introduces a way to track the function of a pressure sensor's cell, which is important but previously had limitations. This method enables reliable detection of potential medium ingress, which can occur through a ventilation channel or membrane rupture.
Problems solved by technology
One problem of capacitive pressure sensors operating according to the quotient method is that a medium ingress—caused by membrane rupture or made possible by an eventual venting channel—could not be detected as a result of the quotient formation, because the dielectric constant εr correspondingly changes in the numerator as well as the denominator.
This problem is further aggravated if the εr of the incoming medium differs only to a minor extent from the εr of air.
Method used
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[0032]In FIG. 1 shows a block circuit diagram of a typical capacitive pressure sensor, which is used for measuring a processing pressure p (for example, of oil, milk, water, et cetera). The pressure sensor 1 consists essentially of a pressure measuring cell 10 and evaluation electronics 20. The evaluation electronics 20 has an analog evaluation circuit 30 and a microcontroller μC, in which the analog output signal of the evaluation circuit 20 is digitalized and further processed. The microcontroller μC provides the evaluation result as a digital or analog output signal, for example, of an SPS. The pressure sensor 1 is connected to a voltage supply line (12-36 V) for power supply.
[0033]FIG. 2 shows a schematic representation of a typical capacitive pressure measuring cell 10, as frequently used in capacitive pressure sensors. The pressure measuring cell 10 consists essentially of a basic element 12 and a membrane 14, which are connected to each other via a solder glass ring 16. The b...
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Abstract
A method for monitoring the operation of a pressure measuring cell (10) of a capacitive pressure sensor (1), wherein the pressure measuring cell (10) has a measuring capacitor (CM) and a reference capacitor (CR) and the pressure measuring value (p) is obtained from the capacity values of the measuring capacitor (CM) and the reference capacitor (CR), characterized in that a control pressure measuring value (p′) is obtained with an auxiliary capacitor (CZ) arranged outside the pressure measuring cell (10) and the operability of the pressure measuring cell (10) is inferred by comparing the pressure measuring value (p) to the control pressure measuring value (p′) is provided.
Description
FIELD OF TECHNOLOGY[0001]The invention relates to a method for self-monitoring a ceramic pressure measuring cell of a capacitive pressure sensor as well as an evaluation circuit for carrying out the method pursuant to the preamble of claims 1 and 2 or claim 9.BACKGROUND[0002]Capacitive pressure sensors are used to measure pressure in many industrial sectors. They frequently feature a ceramic pressure measuring cell as transducer for the processing pressure and evaluation electronics for signal processing.[0003]Capacitive pressure measuring cells consist of basic ceramic elements and a membrane, with a solder glass ring is arranged between the basic element and the membrane. The hollow space between the basic element and the membrane obtained in this way makes possible the longitudinally directed mobility of the membrane as a result of the influence of a pressure. Electrodes, which together form a measuring capacitor, are respectively provided on the underside of the membrane and on ...
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IPC IPC(8): G01L25/00
CPCG01L25/00G01L9/003G01L9/12G01L27/007
Inventor WALTER, HEINZ
Owner IMF ELECTRONIC GMBH